The task of establishing RF communication links is especially challenging in indoor environments because building elements (e.g., concrete, metal partitions) affect radiation patterns in a complex, significant manner. Antenna placement is if critical factor in determining the overall effectiveness of indoor RF communication links and because of the great complexity of the surrounding environment (from the standpoint of RF propagation), trial-and-error methods arc used to arrive at suitable antenna locations.
Due to the significant complexities involved in performing exact RF propagation calculations, various techniques for estimating or predicting RF field strength have been developed. Illustrative examples of propagation models are disclosed in "Ray tracing as a design tool for radio networks", by J. W. McKown and R. L. Hamilton, IEEE Network Magazine, Vol. 5, No. 6, pp. 27-30, Nov. 1991, and "Mechanisms governing UHF propagation on single floors in modem office buildings", by W. Honcharenko, H. L. Bertoni, J. Dailing, J. Qian, and H. D. Yec, IEEE Transactions on Vehicular Technology, Vol. 41. No. 4, pp. 496-504, Nov. 1992. These RF propagation models facilitate the calculation of RF field strength values by implementing one or more simplifying assumptions.
The simplifying assumptions implemented by prior art propagation prediction techniques do not sufficiently enhance computational efficiency for many practical, real-world applications. For example, the ray-tracing prediction technique disclosed in the above-cited article entitled "Ray Tracing as a Design Tool for Radio Networks" is much too time-consuming for the purpose of comparatively and expeditiously evaluating a plurality of antenna locations out in the field. What is needed is an improved approximation technique for analytically characterizing and optimizing indoor RF communications systems. For these applications, it is not generally necessary to have exact agreement between predicted and measured field strength values. Rather, for the purpose of comparatively evaluating several possible indoor communication system design alternatives, it is more important to characterize average field strength values at locations throughout the desired service area.